The present invention relates to novel nuts, especially push nuts, and to fasteners that include push nuts.
Push-nut fasteners include a post of metal or plastic and a push nut that is specially shaped to be pushed onto the post with some effort. Removal of a push nut by pushing it in the opposite direction requires vastly more effort.
A widely used form of push-nut fastener has a nut in the form of a sheet-metal stamping having a hole whose outline includes two or more inward-directed tabs. The innermost edges of these tabs form a circle slightly smaller than the diameter of the post; the push nut is resilient; and the tabs slant toward the center in such a manner that, as the push nut is pushed onto the post, the tab tips lag slightly behind the rest of the push nut. The tabs have sharp corners or edges which tend to dig into the post.
The tabs of such push nuts are sometimes angled in the manner of screw-thread segments so that the push nut might be removed by an unscrewing motion. In practice, it is usually impossible to "unscrew" such push nuts. Moreover, each tab develops a considerable amount of local force tending to distort the post. Such distortion may rule out the use of this kind of push-nut fasteners where the post is a thin-wall tube.
Fasteners having push nuts have been proposed, wherein the push nut is divided circumferentially into multiple sectors each bearing multiple thread segments. Each sector is supported in a yielding manner for providing the push-on characteristic. However, the resulting push nuts are commonly disproportionately large and complicated and, considering their size, the retentive strength seems low.